The present invention is directed generally to peristaltic type pumps and, in particular, to an improved peristaltic pump arrangement for use in minimizing pump start-up problems.
Peristaltic pumps have a wide variety of applications and are often used because of their accuracy in pumping fluids, as well as their relatively inexpensive construction and assembly. Typical peristaltic pumps comprise a rotatable shaft having several circumferentially spaced tube compression rollers supported thereon which are positioned for orbital movement along a circular path against an elastically occludable tube. The tube includes a fluid inlet and an outlet and is positioned between a fixed tube reaction surface of the pump housing and the compression rollers. Peristaltic pumping is effected when the occludable tube is sequentially depressed or occluded by the compression rollers against the reaction surface. In this regard, as the drive shaft rotates, the compression rollers advance relative to the stationary tube to create peristaltic pumping action on fluid within the tube.
A disadvantage of this type of pump is the fact that the occludable tubing is necessarily elastic and will memorize depressions if the compression rollers remain static. Upon restarting there is a tendency for the pump motor driving the pump not to be able to overcome the added resistance caused by these depressions and, thus, the pump cannot operate. Moreover, there are occasional pump/motor mounting misalignment problems which occur in some installations and such variances in the desired alignment create problems in the sense that the drive shaft may encounter added rotational resistance, thereby inhibiting desired pump starting.
Various approaches have been suggested in the peristaltic pump art for addressing problems associated with the cooperation of compression rollers and the associated occludable tubing. Examples of these approaches are shown in the following U.S. Pat. Nos.: 3,353,491; 3,876,340; 3,990,444; 4,025,241; 4,233,001; and, 4,856,972.
Despite the foregoing approaches in this art there is a continuing desire to improve upon the operation of peristaltic pumps particularly in overcoming torque problems.